The Dajjal will be the greatest Fitnah from the time Allah created Adam until the Hour begins.

Saheeh Muslim narrated that Sayedina Hudhaifah (RAA) said that the Messenger of Allah (peace be upon him) said: "I know Dajjal will bring with him two rivers flowing. One will clearly look like water and the other will clearly look like blazing fire. If any of you sees that, let him choose the river which looks like fire, then let him close his eyes and lower his head and drink from it, for it will be cool water."

Saheeh Muslim reported that the Companions asked: "O Messenger of Allah, how long will he stay on the earth? The Prophet (peace be upon him) replied, Forty days: one day like a year, one day like a month, one day like a week, and some of the days like your days." They asked, how fast will he travel through the earth? The Prophet (peace be upon him) replied, like the clouds driven by the wind. He will come to some people and call them, and they will believe in him and respond to him. Then he will command the sky to rain, and the earth to bring forth vegetation, and their cattle will come back to them in the evening, with their humps high, and their udders full of milk, and their flanks stretched. Then he will come to another people and will call them, but they will reject him. So he will leave them and they will be stricken with famine, with none of their wealth in their hands. He will pass by ruins and will say, "Bring forth your treasure" – and the treasure will follow him like a swarm of bees. Then he will call a man who is brimming with youth, and will strike him with a sword and cut him in two, then he will put the pieces apart from one another the distance of an archer from his target. Then he will call him, and the young man will come forward smiling, with his face shining."

Sunan Ibn Majah reported from Sayedina Umamah Al-Bahili (RAA) that the Prophet (peace be upon him) said: "The part of Dajjal’s Fitnah will be that he will say to a Bedouin, Do you think that if I resurrect your father and mother for you that you will testify that I am your lord? He will say, Yes. So two devils will appear to him in the image of his father and mother, saying, O my son, follow him, he is your lord."